HEAT-TRANSFER IN HYDRIDE PACKED-BEDS .3. SIGNIFICANT INTERACTIONS BETWEEN THE TEMPERATURE AND COMPOSITION GRADIENTS

Two types of experiments are reported, in order to study the coupling between heat transfer and the hydriding reaction. One series operate with the LaNi5-H-2 system in a closed reactor submitted to heating/cooling cycles. The second is achieved with complete and slow hydriding/dehydriding reaction. These experiments are simulated by a numerical model of the heat transfer in the whole reactor, with validated assumptions. In both procedures, the simulation results agree with the experiments. The analysis shows that the temperature gradients induce composition gradients within the hydride bed, making the local temperatures, compositions or reaction rates very different from the averaged values. The coupling between heat transfer and reaction induces significant effects that cannot be explained otherwise.